Sanding drum



Nov. l, 1932. c. 'MAT'nsoN SANDING DRUM Filed Jan. 4. 1929 Patented Nov. l, 1932 UNITED STATES PATENT oFFicE .CARL LAWRENCE ivrnrrrsonjor :aocxronn, JLLINoIs, AssIGNoa ToV ivrn'rrrson MACHINE Wonne. or nocxronn, ILLINOIS, yA-conroan'rron or ILLINOIS sANnINe Daun Y 1 pplication led January 4, 1929. Serial No. 330,206.

I This inventionrelates generally to sandingV drums and in `particular to rotary sanding drums embodying mounting, clamping and tensioning means for the sheets operatively associated therewith. i

lGenerally a dominating object of the invention is to provide a sanding drum which may be easily and simply constructed and assembled to obtain apermanent, substantially7 perfect, balance.v v

In connection with the'foregoing object, a

further object resides in the .provisionof sheet.

mounting clamping andtensioning structures incorporated 1n the drum which are separable from the drum for easy assemblyror replacementV and which maybe vsupplied as individual units.

Another Object ofthe inventan is to pro-v vide structures for operating upon the workingsheets in the form ofa series of` units each of which may be supplied for'installation in a drum in a previously balanced andcentered condition whereby the original balance of the drum` will not beimpaired. y Y

Still another object of theinvention is to provide a construction which facilitates the replacementk of paper andpadding by profie viding a new and improved paper clamping and tensioning means,as wellas a simple means for taking up slack in the padding.

Other objects and advantages will become apparent in the following description vand from the accompanying drawing in which:.

Figure l is a longitudinal cross section partially in elevation of a 'sanding drum embodying the construction by which the features of the invention are attained.

Fig. 2 is a transverse section along 2 2 of Fig. 1.

Fig. 3 is a transverse section taken `substantially on the line 3,-3 of Fig. l illustrating one of the clamping structures.

Fig. 4 is a similar transverse section taken on the line 4-4 of Fig. l toillustrate one of the tensioning structures.

Fig. 5 is an enlarged fragmentary detail of the padding adjusting means.

I/Vhile thfe invention is susceptible' of various modifications and alternative constructions, -I have shownr in the drawing and. will the line .I

herein describein detail the preferred'embodiment, but it is to be understood that I do` not thereby intend to limit the inventionetjothe specific form-disclosed, but intend to cov-k er allmodifications and alternative constructions falling within the spirit and scope of the invention as expressed in the 'appended' Inprior constructions,of the type to which' this invention is pertinent, it has been customary to place a layerof padding suchas felt..

between the drum and the sheet `of abrasive papeny It has been found in Lpractice that the continued action ofthe rotatingv drum on the v work causes the layer of feltpaddingto' stretch and loosen `circumferentially ofthe drum. :In-addition, the abrasive sheet .also stretches similarly' and further looseness thereof is-caused by the-'decrease in thickness of the stretched felt thereby producingcon-v siderable slack in the abrasive surface.,

. In attaining the objects of the invention itk may be stated at lthe outset that the preferred sanding drum construction illustrated herein is adapted to overcome-such'slackness, and,

tially the length ofthe drum and are ar-v ranged for simultaneous actuation by a common means to engage or release bothy ends of the abrasive sheet, the body of which is wound about the drum. The-tensioning structures eXtendentirely across the length of the drum and are also capable of actuation by a com.- mon means to remove them from their tensioning engagement with the paper.` i

Each of the clamping and tensioning structures, however, areV independently held in Operative engagement with the paper to pro- ISG miy

vide, in the case of the clamping structures, a positive clamping action throughout the length of the paper regardless of variations in the thickness thereof, and to insure, in the case of tensioning structures, that each portion of the abrasive sheet throughout the length of the drum will be held under proper tension without respect to irregularities in stretching or unevenness of the felt padding. In additiomthe mounting means for incor-y porating the padding upon the drum includes an adjustment by which slack in the padding may be taken up from time to time as it becomes necessary. c v

More particularly describing the invention, a drum is indicated which is preferably made of cast iron which may be closed at each end by end plates 10a secured thereto in any suitable manner. lnteriorly ofthe drum a number of spaced integrally formed transverse websv11 are provided with centrally positioned supporting bearings 12 for mounting` a supporting shaft 13. The drum is rigidly mounted on the shaft in any mannery which gives a certain degree of permanence, as by finishing the bearings to provide a driven fit for the shaft. Y

The drum has a longitudinal gap 14 defined at one side by an edge 15 of the drum body and on therother side by a cast iron structure 16 which is substantially triangular and prismatic in shape. This structure is'a removable section of the drum and has an arcuate surface 17 forming a section of 'the drum periphery and further has an in- 5 21 entering the webs 11 are provided for securing the section 16 to the drum proper.

The mounting and adjusting means for the padding The felt sheet 22 which is preferably used in padding the drum is arranged to besecured rigidly at the leading edge of the open seam in the drum and for take-up adjustment at the trailing edge of the drum since in operation any looseness in the padding tends to work its way toward the trailing edge. 'lo this end'an elongated screwed cl-eat or strip 23 engages one end of the padding sheet to clamp the padding between the cleat and the bottom of the groove 19 formed near the arcuate surface of the removable section. Y

The padding is then wound about the drum and enters the seam therein at the trailing I edge 15. This end of the padding is secured between .a pair of elongated bars 2li (Fig. 5) as by means of the screws 25, the bars in turn being mounted for movement as a unit toward and from the seam by means of screw threaded engagements with properly formed tervals along the bars preferably at points adjacent the adjusting screws26 to bear against the webs thereby insuring rigidity of the assembly. By this construction the 4padding layer may be easily mounted, on vtheV drum and adjustment to take up the slack is effected by first loosening the set screws 29 and then tightening the elongated screws 26 to draw the padding to proper tension, after which the set screws may again be `brought into engagement with the webs.`

rihe paper clamping and tensioning means in the present embodiment are varranged to be disposed longitudinally of the shaft 13 in such manner as tov permit limited swinging motion relative to the shaft to perform their respective functions. As has been mentioned each means comprises a series of similar structures, the numberof which depends upon the length of the drum, mounted in alternating relation; that is, a single structure of one series is positioned on the shaft between two structures of the other series. inasmuch as the structures of each series are substantially the same, only one of each will be described in detail. i

The paper clamping means Referring to Figs. 1,2 and especially Fig. 3, the clamping member comprises a structure substantially in the form of an arm 30,

mounted on the shaft 13 and carrying a clamping head 31 swingable to and from the recess of the removable section 16 to grip the ends of the sheet of paper between the removable structure and the head. ln this embodiment the clamping structure is cast in complementary semi-circular hub portions adapted to receive the shaft 13 relatively snugly therebetween. Lugs 3ft formed integrally withthe sections adjacent the abutting sides of the semi-circular sections'are adapted to receive screws 35 for securing the two sections together with the shaft therebetween. This construction permits the clamping members to be assembled on or removed from the shaft after the shaft and drum are rigidly united. Y

The arm 30 extending from the hub portion spaces the clamping head an appropriat;y distance from the hub, the'head being substantialiy elongated and extending longitud ly of the drum. if desired the engaging race .Lele

" the. removable drum section on the head may beknurled to form a more positive paper engaging surface.k

. The clamping head is vpreferably pressed toward its clampin present embodiment, this end irs-attained by forming a boss 36 integral with one of the lugs 34 on the upper section, Vas uponthe left seat fora relativelyl stiff helical spring 38 which at its free end 4carries a flat headed pinl I 39 having its stem fittinginto the spring'.

Each o-f the transverse webs of the drum is provided with aligned apertures which receive and form Vbearings for a clamping cam shaft 40 which runs the full length of the drum and` is positioned'substantially adjacent the flat heads of the pins 39.' At points adjacentthese flat heads, cam surfaces are formed on the shaft by flattening the shaft substantially to Val semi-circular cross section ask shown at 41. The cam shaft 40 `has la squared end 42 (Fig. 2) to which awrench` or other suitable tool may be applied for turning the shaft tomove theiflattened portions of the cam shaft into and outof engagement with the series' of pins 89. f Thus when the cam shaft40 is turned with the rounded surfaces of the shaft bearing against thevpins 39 the springs 38 will be simultaneously tensioned tvo-swing the series of'clamping members 30 about the shaft thereby moving the'clamping heads 31 into close abutment with the recess 20 in.' the removable drum section 16.

Contrarily when the shaft is rotated to op-l pose the flattened surfaces 41 to the pins, the tension of the springs 38 is relieved and the clamping heads may be swung away from the recess 20 to release the paper.

In forming the recess 20 in the removable section, it will be seen (Fig. 3) that the edge of the removable section is cut away thereby forming, with the web when assembled, shoul-y ders 42 on each of the webs which serve to locate the position of the paper as vit is applied to the drum.

In the operation of mounting the abrasive sheet 43 on the drum, the cam shaft 40 is turned to relieve the holding tension of the springs 38 after which the clamping heads may be swung out of engagement to permity the removalof the old and worn paper from drum. A fresh sheet of paper is then wound about the drum starting at theleading 'edge of the drum with the edge of the paper abut ting the stop shoulders 42. The trailing edgev of the paper crosses or spans the open seam between the section 16 and the drum edge 15 and is brought into juxtapositionwith the leading edge of the paperv between the section 16 and the clamping heads 31. Rotation of the cam shaft to tension the springs swings the clamping heads simultaneously to clamp the engagement with 16 and, Vin the.

two ends of thepaper between the heads'andk the removable sectionbof the'drui'n.- a

Counter-balancing weightsin the yform' l lugs v44 and 45 formed integrally with the lower section 33`at` points diametrically op-v posite from the clamping head 31 andthe boss 36 insure that each of thestructures may be perfectly and individually balanced. i 'y The paperltcnsioningmeaiis The tensioning means as shown-in Figs. 1, 2 and particularly Fig-4 is also in the form of a swinging larm and is'cast in upper and lower sections 46 and 47v corresponding, as faras the two semi-circular hub portions and securing lugs 34a are concerned, to the construction of the hub portion of the clamping-v Thus each individual tensioningf also be removed or replaced'l about the, shaft of the drum without disturb-y members. structure may .ing the rest ofthe assembly.

The upper section of the tensioning struc:V 48 which preferably is ture carries Vthe arm integrally formed on the upper sectionofthe hub and, at its upper end, supports a longitudina-lly extending tensioningblade 49 positioned to engage the abrasive sheet at an appropriate point intermediate the trailing edge of the drum and the clamping head the swinging movementy of the tensioning structureabout the shaft in one direction', the

blade is arrangedito exert a pullingforce away from the edgek of the vdrum and substanf- 31.7V Moreover, the. arrangement is such that, in

a helically coiled spring 50 bearing between the side of the arm 48 corresponding-to the trailingV edge of the drum V.and a lug 51 formed integrally on they inner surface of the drum. Guide pins s2 onthe arm'and'lug,

aboutV which the spring is seated, maintain the spring inoperative relation with respect` to the arm and lug. A tensioning cam shaft 5,4 which may be similar inform andconi struction Atothe clamping cam shaft` 42 is rotatably mountedin the4 webs toextend thek full length of the drum -adj acent to the sides of the series of rarms 48opposite the spring mounting.

The tensioning cam shaft has flattened sur-y faces 55` movable, upon rotation of ythe shaft, into position opposite the adjacent sidesof the arms A48 to free the arms from the arcuate surfaces of the cam shaft and allow the tension ofthe springs 51 to force the tensioning blades into engagement with the abrasive sheet. This, in the operation ofthe drum,

is the vnormal positiony of the -fsh'aft,

thus permitting the tensioning blades. to ,be 'i constantly urged lin the V,paper tightens" ing direction. Rotation of the shaft brings the arcuate surfaces thereof into engagement with the sides of vthe V:arms

an old and insertion of a fresh abrasive sheet.

' will be held under tension.

The lower section of eachtensioning structure carries a counter-balancing weight 5G disposed substantially diainetrically from the arm 48 and plate 49 on the upper section to permit the structures to be individually balanced.

. It may be seen, from a comparison of the positions of the tensioning blade, as shown in Figs. 2 and 3, that the blade may, when Considerable slack has been taken up in the paper, swing past the clamping heads. To permit this, the ends of the clamping heads are spaced apart a sufficient distance to allow the arms 48 of the tensioning structures to pass therebetween. The tensioning blades, however, are preferably of such length that the ends thereof nearly abut, thereby insuring that each portion of the abrasive sheet lt has also been found desirable to form the clamping structures for the extreme ends of the drinn as right and left hand members 30 and 30h. These however are substantially the saine as the center structures except for the shorteningof the head on one side of the arm.

Assembly cmd balancing operation In assembling the various parts to form a complete operative structure the drum 10 is first secured upon the shaft 13 and the triangular removable section 16 is secured to the drum. This assembly is next mounted for a machining operation, in a welleknown inanner, and the peripheral surface of the drum is t-rued or finished to the aXis of the shaft. In forming the drum, the webs and other parts formed integrally therewith, are disposed in such manner about the interior of the drum that the drum, shaft and removable section, when assembled, will be nearly balanced. During the finishing operation the balance of the drinn about the axis of the shaft may be further corrected to place the assembly substantially in perfect balance.

The tensioning and clamping structures are finished and balanced separately by mounting each one individually upon a separate shaft of substantially the saine diameter as the shaft 13 and finishing them to a substantially perfect b-alance about the shaft. Thus when each of the individual structures are secured to the shaft in the drum the resulting structure is true and balanced. An

important advantage resulting from the separate balancing of each of the individual structures resides in the fact that any structure in the drum may be removed and replaced by another structure without disturbing or in any way interfering' with the balance of the drum.

. Operation Briefly recapitulating the operation of the drum, it is assumed that the abrasive surface is worn out and that the padding layer 'is slightly loose. To replace the paper, theoperator first rotates the tensioning cam shaft 511 to swing the tensioning blades to their remote position and then rotates the clampingv cani shaft 10 to release the tension of the clamping springs 38. rlhe paper clamping members may then be pushed to their disengaged position and the worn paper withdrawn from the drum. This exposes the adjusting means for the padding, which may be tightened to a desired tension in the manner previously set forth. A fresh piece of abrasive paper is then placed about the drum in position to lbe clamped and rotation of the clamping cam shaft swings the clamping heads into engagement with the paper. Subsequently, release of the tensioning means through rotation of the tensioning cam shaft effects a proper tensioning of the paper. y

When it becomes necessary or desirable to replace any of the paper clamping or tensioning structures in the drum the operation may be simply and easily performed. The paper and padding strips are first removed from the drum which exposes and permits removal of the triangular drum section 16. Thus a substantially large gap Vis provid-ed in the drum allowing access to the screwsv 35 to separate the hub sections and free the desired structures from the shaft. A new and predrum, after which the drum is again in per- 4;

fectly balanced condition for use.

It will be apparent from the foregoing description that a sanding drinn has been provided in whicha substantially perfect balance is readily possible, which balance remains true even though replacement of various of the paper working elements may become necessary.

l claim as my invention:

1. A sanding drum comprising, in combination, a shaft, a drum mounted rigidly on said shaft ,having an external surface for presenting an abrasive sheet to a piece of work, a plurality of clamping structures including longitudinally extending clamping heads mounted on said shaft for relative swinging movement into and out of clamping engagement with the sheet, a plurality of tensioning structures including longitudinally entending sheet-engaging tensioning heads mounted alternately on said shaft with respect to said clamping structures and also swingabley for engagement with said sheet, said clamping heads being` shorter than the tensioning heads to permit swinging tensioning heads past said clamping heads.

movement of said 1 'arm and extending substantially at right angles therefrom, a spring seated on said boss, and a shaft having camksurfaces thereon Vengaged by Vsaid spring for compression or releaseof tension to swing said head` into or( permit movement lthereof away from its clamping position.

3. A sanding drum having, in combination v with a hollow split cylinder mounted for rotation with a shaft, a tensioning element for maintaining a clamped abrasive sheet in proper tension comprising-an arm mounted on said shaft for relative rotational movement relative thereto, a tensioning head carried by said arm and extending'longitudinally of the cylinder near the split therein, a resilient member interposed between said arm and a s'tationary'pa-rt of said cylinder normally tending to move said arm and headin a sheet tensioning direction, and a shaft having cam surfaces thereon positioned to engage the oppositeside of said arm and upon rotation of said shaft to. move said arm against the tension of said resilient member. y Y

et. In a sanding drum, the combination with a split cylinder mounted for rotary movement, of means for holdinga padding strip about the external surface of saidV cylinder and for adjusting the tension thereof comprising a meansfor securing one end of the padding strip within said cylinder at the leading edge of the split, a pair of bars clamping the other end' of said strip therebetween, an means for adjustably securing said barswithin said cylinder including screws through said bars engaging portionsof said cylinder to draw the bars into the cylinder, and'set screws to prevent movement of the bars after adjustment.

5. A sanding drum having, in combination with a hollowsplit cylinder mounted Vfor rotation; with the shaft, a plurality" of sheet clamping structures detachably mounted within said drum on said'shaft, a plurality of sheet tensioning structures also detachably mounted within said Vdrum on said shaft in alternating relation with said sheet clamping constructions, each ofsaid sheet clamping and sheet tensioning structures having tion with a hollow split cylinder mounted for Y rotation with the shaft, a plurality of clampin devices includin sheet en a inomemg a bers mounted on said shaft for swinging movement relative thereto 'to position said members in or out of clamping engagement with a sheet, a plurality of tensioning structures each including a sheet engaging head also mounted on said shaft for swinging movement to position said heads inor out of engagement with said shaft, said clamping structures and said tensioning structures being disposed along said shaft in alternating relation, said sheet engaging members on the clamping structures being spaced from each other to permit passage of said tensioning structures therebetween in the swinging movement thereof. y l

In testimony whereof, I have hereunto affixed my signature.y 1 Y CARL LAWRENCE MATTISON.

counter-balancing weights formed thereon to permit each structure to be individually balanced about the aXis of said shaft. Y i 6. A sanding drum having, in 'combina- 

